Elastic System Fibers in the Mandibular Connective Tissue of Blotchy Shark: Ultrastructural Study pp. 379-392
Authors: (Takashi Sawada, Sadayuki Inoue, Department of Ultrastructural Science, Tokyo Dental College, Mihama-ku, Chiba City, Japan, and others)
Abstract: For the study of the role of the elastic system fibers in the movement of eruptive teeth in the shark mandible, the connective tissue of the mandible was examined ultrastructurally and immunohistochemically. A tooth-bearing mandible was dissected out of a shark, Cephaloscyllium umbratile, and further processed for light microscopy, thin section electron microscopy and immunohistochemical staining. The connective tissue of the mandible was divided into three successive layers (zones): an area immediately below the oral epithelium (zone 1), a broad central layer of dense connective tissue (zone 2), and a layer of loose connective tissue next to the perichondrium rich in well developed blood vessels and nerves (zone 3). Elastic system fibers were composed of oxytalan, elaunin and elastic fibers, and were uniquely distributed in the tissue according to their functional roles. Oxytalan fibers were scarce in zone 1, but were abundant in zone 2 among bundles of collagen fibrils and often close to fibroblasts. Elaunin and mature elastic fibers were localized mainly in zone 3, and the former was concentrated in areas surrounding blood vessels. Both oxytalan and elaunin fibers were intensely immunostained for fibrillin, while mature elastic fibers stained poorly. Oxytalan fibers were concentrated mainly in the outwardly moving tooth band (zone 2), and since microfibrils, their constituent, are known to be abundant in the body in areas exposed to stress, these fibers are likely to provide mechanical strength to the tooth band for the successful movement of eruptive teeth. The role of elastic fibers and elaunin fibers in zone 3 may be for the absorption of shock within the tissue caused by the movement of eruptive teeth, and protection of the integrity of the vascular system in the connective tissue, respectively.
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